Reactive compensation device and method for partially regulating voltages and capacitance of three-phase four-wire power grid

The invention discloses a reactive compensation device and method for partially regulating voltages and capacitance of a three-phase four-wire power grid. The reactive compensation device comprises a U-phase voltage and capacitance regulating reactive compensation unit, a V-phase voltage and capacitance regulating reactive compensation unit, a W-phase voltage and capacitance regulating reactive compensation unit and a control unit. Each phase of voltage and capacitance regulating reactive compensation unit is mainly composed of a current detection element, a voltage detection element, a full-voltage compensation capacitor bank, an auto-transformer and a voltage-regulating capacitor bank. The control mode of independent reactive compensation in each phase is used in the three-phase four-wire power grid, total capacitance in each phase is uniform, the capacitance in each phase is evenly divided into n sets, wherein one set of the capacitance is subjected to voltage and capacitance regulation through the auto-tr